1. Field of the Invention
The invention relates to a process for the production of a seasoning sauce similar to soy sauce.
2. Description of Related Art
It is well known to produce soy sauce by a fermentation process in which soybeans, in the form of whole beans or crushed, defatted soybeans, and optionally wheat, usually in the form of a roasted, crushed grain, and salt are used in varying proportions, and, on the basis of the kind of malt an enzyme-containing, fungus-covered substrate, referred to as koji, is produced. This is then mashed with salt water and subjected to a multi-step fermentation, comprising a hydrolytic process with lactic acid and alcoholic fermentation, followed by a maturing phase. The fermentation organisms used are the hypha fungi of the strain Aspergillus oryzae or Asp. soyae for the koji production, as well as the salt-tolerant lactococci Pediococcus halophilus and the yeast Zygosaccharomyces rouxii in the fermentation phase.
Contrary to former methods, where the natural accompanying flora effected the fermentation, modern processes use defined starter cultures. In the case of genuine, fermented sauces, no mineral acid is employed for accelerating the decomposition of the raw plant materials. This is done exclusively by means of enzymatic hydrolysis effected by the fungal enzymes formed during the koji phase. In recent developments, immobilized enzymes or immobilized microorganisms are used for fermentation. However, when the fermentation period is shortened and the salt contents are reduced during mashing, the taste qualities of the sauces thus achieved are not as good as those produced according to the former process. After a prolonged maturing phase (3 to 6 months) the mash is refined by squeezing, heating, turbidity sedimenting and precoat filtration so as to yield a stable ready-to-eat sauce. Traditionally prepared soy (shoyu) sauce has a dark color and a salty, full, roasty and malty flavor which is somewhat unfamiliar to Western taste.
JP-A-52-76488 describes a process for the production of a seasoning sauce on the basis of protein-containing raw materials such as soybeans, soybean protein, wheat, barley, wheat gluten, corn gluten, fish protein, milk protein, etc., and carbohydrate-containing raw materials such as sorghum, rice bran, wheat bran, potato, molasses, starch residues, etc., from which a koji is made using suitable koji organisms such as Aspergillus soyae and Aspergillus oryzae, which is fermented in a saline solution at temperatures between 30.degree. and 55.degree. C.
U.S. Pat. No. 4,115,591 describes a process for the production of a koji wherein a koji fungus is cultivated in a modified koji substrate at a temperature of 20.degree. to 40.degree. C. for 30 to 100 hours in the presence of 0.05 to 8% of a salt of an aliphatic carboxylic acid having up to four carbon atoms. The koji substrate is selected from the group consisting of soybeans, defatted soybeans, gluten, rice, wheat, wheat bran, barley, oats, corn, fish meal and other products. The resulting koji is used for producing fermented food products such as soy sauce, miso and sake, by fermentation in a 22% salt solution at 30.degree. C. for 150 days.
EP-A-417 481 describes a process for the production of a soy sauce by fermentation on the basis of a koji produced by fermenting a mixture of crushed soybeans and wheat by means of a koji culture, according to which the koji is hydrolyzed in aqueous suspension with the enzymes obtained during the fermentation with the koji culture, at 45.degree. to 60.degree. C. for 3 to 8 hours, whereupon the mixture is subjected to a four to eight-week fermentation after the addition of sodium chloride in an amount necessary to obtain a salt content of 15 to 19%.
As regards the prior art, reference is also made to U.S. Pat. No. 3,912,822, which describes a process for the production of a protein hydrolyzate having a high glutamic acid content by means of a proteolytic enzyme.
An object of the present invention is to produce a seasoning sauce similar to soy sauce but which has a lighter color, is less roasty in flavor and more neutral but harmonious so as to be better adapted to the Western trend of taste, and which also has a salt content as low as possible. Another object is to shorten the production process to a period of less than 3 months.
It has been surprisingly found that the problems which currently exist can be solved by means of certain process control using raw materials not traditionally employed for soy sauce fermentation, namely by using an enzyme-containing fungus-covered substrate (koji) consisting of dehulled and soaked oat grains. According to the invention, such a koji is mashed with a brine relatively low in salt, and the fermentation is then carried out in several steps.